Fire detection system



Nov. 10, 1953 M. F. PETERS 2,659,067

FIRE DETECTION SYSTEM Original Filed May 2, 1949 M /3 i INVENTORMELV/LLE E. PETE/Pd BY q ATTORNEYS Patented Nov. 10, 1953 FIRE DETECTIONSYSTEM Melville F. Peters, East Orange, N. J., assignor, by mesneassignments, to Samuel Scrivener, J r., trustee of the Petcar TrustOriginal application May 2, 1949, Serial No. 90,881, now .Patent No.2,586,252, dated February 19, 1952. Divided and this application January15, 1952, Serial No. 266,563

The portion of the term of the patent subsequent to February 19, 1969,has been disclaimed 3 Claims. (Cl. 340-227) This application is adivision of my co-pending application Serial No. 90,881, filed May 2,1949, now Patent #2586252, for Fire Detector Element, which is itself acontinuation in part of my application Serial No. 2,345, filed January14, 1948, for Fire Detector Element, which is now abandoned.

This invention relates broadly to fire detecting systems and deviceswhich are placed within a space which is to be monitored for fires andwhich operate to provide a signal or alarm when combustion occurs. Moreparticularly, the invention has to do with that class of such deviceswhich operate on an increase, to some predetermined value, in theambient temperature within the monitored space and applied to a part ofthe system or device, as distinguished from fire detecting devices whichare caused to operate by the light emitted by a flame, or by the effectof smoke on a photoelectric cell, or in other known manner.

The invention consists in the provision of a fire detector in the formof a readily bendable tubing element of indefinite continuous lengthhaving within it and spaced from it and from each other two continuousun-insulated electrically conductive Wires which are maintained inspaced relation to each other and to the surrounding tubing by adiscontinuous element which fills the tubing and surrounds and engagesthe conductors and which is formed of a material which is non-conductiveto electricity at normal temperatures but becomes electricallyconductive at some predetermined abnormal temperature such as that ofthe combustion of some selected material. an alarm or signal systemwhich is closed to operate the signal or alarm by completion of thecircuit between the two conductors when the normally non-conductivematerial becomes conductive on heating.

Other results, advantages and new features of my invention will be madeapparent by the description and drawings forming part hereof but whichare solely for the purpose of describing one embodiment of my inventionand therefore impose no limitation on the invention not specificallystated in the claims.

In the drawings,

Fig. 1 illustrates part of an airplane, showing a fire detector elementled through parts thereof;

Fig. 2 illustrates a detector element according to this inventionincluded in the circuit of an electric fire detection system;

Fig. 3 illustrates part of a fire detector element according to thisinvention, part of the protective The two conductors are connected incasing being broken away, and part of one of the beads bein broken away;

Fig. 4 is a sectional view taken on line 44 of Fig. 3, and

Fig. 5 is a cross-sectional view similar to Fig. 4

but showing a modified form of the invention.

In Fig. 1 of the drawings there is shown, for illustration only, how acontinuous fire detector element such as that provided by the inventionmay be employed to monitor a space in which fire may occur. here shownas being led through the engine nacelle 4, wings 6, 8 and fuselage 9 ofan aircraft and, upon undesired increase in the ambient temperature atany point along the length there- 1 of, will operate in the mannerdescribed hereinafter to operate a signal or alarm I I providing a Ywarning to the pilot. Obviously any other type of structure or space,such a room, baggage hold, etc. may be monitored with the same apparatusand with the same results.

The fire detector element 2 is shown in Figs. 2, 3 and 4 and comprises areadily bendable tube .IO of indefinite continuous length Within whichare two spaced, parallel, electrically conductive wires [2, M, which aresurrounded, supported and held permanently in space relation to eachother and to the tubing ill by a dis-continuous j .element [3 fillingthe tube throughout its length and consisting, in effect, of a pluralityof separate beads l6 which are formed on and fused to the conductors,are spacedalong the length thereof,

and which are of such size as to fill the tubing.

.The conductors l2, M are preferably made of stainless steel or Inconelbut may be formed of other suitable material. The tube In may be formedof any material which is a good heat conductor.

The discontinuous element which supports and spaces the two conductorsis made of a material preferably formed and fused to the conductors bythe method disclosed and claimed in my United States Letters Patent No.2,495,867 dated January 31, 1950, and in the drawing they are shown asthey are actually formed by such method.

In such a method, the two conductors are encased in a cylinder ofthermistor material which includes an inert ceramic ingredient such as isteatite'and an ingredient which is removed by The fire detector element2 is i heating. Alternatively, the cylinder may comprise thermistormaterial together with the inert ceramic compound, the thermistormaterial taking the form of one or more metallic organic compounds whichdissociate on heating. In either event, when the cylinder is subjectedto heat, the ceramic material shrinks into the formof closely spacedbeads, which firmly adhere to the conductors to provide good contacttherewith. The small spacing between adjacent beads permits the beads toaccommodate themselves to bending of the casing about small or largeradii while at the same time the beads cover the greater parts of thelengths of the two wires. The tubing and beads are preferably circularin cross section but may be made elliptical, in which case the wires areplaced within the major axis of the beads as clearly shown in Fig. 5.

In an embodiment of the invention which has been constructed and isoperated successfully, two Inconel conductors, each of which is .010inch in diameter, are embedded in beads having an outside diameter of.050 inch. In this element the conductors are spaced .010 inch wall towall, and the minimum distance between the periphery of each conductorand the outer surface of the heads is .010 inch. Such an element is sothin that it may be bent on very small radii without dimculty andwithout danger of breaking the conductors or loosening them from thesurrounding beads. If the spacing of the wires is materially increasedabove that stated above it may be desirable, but perhaps not necessary,to malre the tubing and beads elliptical in cross-section, placing theconductors in the major axis of the cross-section, as shown in Fig. 5.In such an embodiment of the invention, the elliptical beads may haveexterior dimensions of .050 inch and .040 inch, and the conductors maybe .010 inch in diameter. By making the beads elliptical incross-section resistance to bending about any axis other than oneparallel to the major axis is created and in all normal, unforcedbending of the elliptical detector element only such bending will takeplace, thus insuring equal bending of the conductors.

As illustrated in Fig. 2 the conductors l2, M .of the detector elementmay form part of an electric circuit including battery 30, signal 32 andtest switch 34. In normal operation and use the test switch is left openand the signal 32 is therefore normally de-energized. If any part of theelement, for example part A, is subjected to a predeterminedtemperature, which may be that of combustion of gasoline, the electricalresist ance of the material of which the beads are formed is so reducedthat electric energy flows through the bead or beads, and thus betweenthe two conductors, at location A, completing the circuit throughbattery 30, signal 32 and those parts of the conductors l2, 14 betweenlocation A and the battery and signal, thus energizing the signal. Whenthe predetermined temperature at location A is removed, for example byputting out the fire, the resistance of the beads will revert to itsnormal high value and no current will flow in the alarm circuit. Theenclosing and protective tube l may or may not be grounded. In eithercase small parasitic currents will flow between each conductor and thetube on operation by heating but these will not in any way affect theoperation of the device or the system.

The term normal temperature is used herein as defining a temperaturelower than that which is generally known in the art as flame tempera- '4ture, and the term abnormal temperature, as defining flame temperatureor a temperature higher than the same, or a predetermined temperaturewhich is to be detected and which is higher than the normal temperature.

While I have described and illustrated but one embodiment of theinvention, it will be apparent to those skilled in the art that otherembodiments, as well as modifications of those disclosed, may be madewithout departing in any way from the spirit or scope of the invention,for the limits of which reference must be made to the appended "claims.

What is claimed is:

1. A system for indicating the existence of a predetermined abnormalhigh temperature comprising a readily bendable cable-like element ofindefinite continuous length comprising a bendable tubing element formedof material of relatively high heat conductivity, a unitary assemblydisposed within the tubing element and being in heat-transfer relationthereto but being separate therefrom and comprising two electricallyconductive uninsulated wires which are substantially co-extensive inlength with the tubing element and are spaced therefrom and from eachother throughout their lengths, and a member formed of a material whichis substantially nonconductive to electricity at normal lowertemperatures and which becomes conductive to electricity at abnormalhigher temperatures surrounding and adhered to said wires and whichmaintains them in closely spaced relation to each other and tightlyengages the interior surface of the tubing element to provide anelectrically conductive path between the wires in substantiallyinstantaneous response to abnormal higher ambient temperatures to whichthe exterior of the tubing element may be subjected, while electricallyinsulating the wires from each other at normal lower temperatures, asource of electric energy and an indicating means electrically connectedto each other and to said wires at one end of said element whereby theexistence of a pre-determined high ambient temperature at any locationalong the length of the cable-like element will cause the temperatureresponsive member thereof to establish an electrically conductive pathbetween the wires at said location to complete a circuit through thetemperature responsive member, the wires, the source or electric energyand the indicating means to energize the indicating means.

2. A system for indicating the existence of a predetermined abnormalhigh temperature com prising a readily bendable cable-like element ofindefienite continuous length comprising a bendable tubing elementformed of material of relatively high heat conductivity, a unitaryassembly disposed Within the tubing element and being in heat-transferrelation thereto but being separate therefrom and comprising twoelectrically conductive uninsulated wires which are substantiallyco-extensive in length with the tubing element and are spaced therefromand from each other throughout their lengths, and a member formed of amaterial which is substantially non-conductive to electricity at normallower temperatures and which becomes conductive to electricity atabnormal higher temperatures surrounding and adhered to said wires andwhich maintains them in closely spaced relation to each other andtightly engages the interior surface of the tubing element to provide anelectrically conductive path between the Wires in substantiallyinstantaneous response to abnormal higher ambient temperatures to whichthe exterior of the tubing element may be subjected, while electricallyinsulating the wires from each other at normal lower temperatures,indicating means, a source of electric energy normally unconnected tosaid indicating means but connected thereto through said member toenergize the indicating means upon increase to a pre-determined degreeof the temperature at any location along the length of the cable-likeelement to establish an electrically conductive path through said memberbetween the wires at said location.

3. A system for indicating the existence of a pre-determined adnormalhigh temperature comprising a readily bendable cable-like element ofindefinite continuous length comprising a bendable tubing element formedof material of relatively high heat conductivity, a unitary assemblydisposed within the tubing element and being in heat-transfer relationthereto but being separate therefrom and comprising two electricallyconductive inunsulated wires which are substantially co-extensive inlength with the tubing element and are spaced therefrom and from eachother throughout their lengths, and a member formed of a material whichis substantially nonconductive to electricity at normal lowertemperatures and which becomes conductive to electricity at abnormalhigher temperatures surrounding and adhered to said wires and whichmaintains them in closely spaced relation to each other and tightlyengages the interior surface of the tubing element to provide anelectrically conductive path between the wires in substantiallyinstantaneous response to abnormal higher ambient temperatures to whichthe exterior of the tubing element may be subjected, while electricallyinsulating the wires from each other at normal lower temperatures, asource of electric energy, and indicating means connected to beenergized by said source by electrical connection of said Wires throughan electrically conductive path through the temperature responsive meansby reason of the existence of a predetermined high ambient temperatureat any location along the length of said cable-like element.

MELVILLE F. PETERS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,483,793 Thomas Oct. 4, 1949 2,586,252 Peters Feb. 19, 1952

